Method and device for splicing two thin webs of material

ABSTRACT

In a device for splicing two thin film web portions comprising a roll supplying a web of film material, a roll for winding a web of film material and a splicing table adapted to be subject to sub-atmospheric pressure and having a first groove therein defining a cutting line and a reel for applying a splicing tape to unite said first and second webs of film, the splicing table includes a second groove that is parallel to the first groove, both grooves being perpendicular to the longitudinal direction of the webs of film, the vacuum table being thus split into three regions each individually adapted to be put under sub-atmospheric pressure, the device being useful for highly accurate splicing of webs of ultra-thin film material.

BACKGROUND OF THE INVENTION

The present invention relates to a method for splicing a first length orweb of film material to a second web of film material. It also relatesto a device for carrying out the said method comprising a roll forunwinding a first web of film material to be spliced, a roll for windingfilm material to be spliced and a splicing table subjected to vacuum andhaving a cutting groove over which the web of film to be wound orunwound can pass, together with means for applying an adhesive splicingtape.

The splicing of two extremely thin films is a difficult operationinvolving problems not only in making the actual splice, but also inensuring that the splice obtained is sufficiently reliable and does notin any way alter the behavior of the thin film material duringsubsequent processing (application of metallization to the film surface,or even reading and/or writing of information on said film afterapplication of a magnetic material coating thereto) or during winding orunwinding. It is in fact an extremely difficult operation to accuratelyapply a narrow tape of adhesive film simultaneously onto two preparedend portions of film strip, principally as as a result of thesignificant electrostatic forces that exist between the two end portionsof the static-charged film, prior to bringing the adhesive tape intobonding contact with said film, such electrostatic charges almost alwayshaving the effect of causing one of the three elements involved in thesplicing operation to move with respect to the two others prior tobonding contact being able to be achieved. Moreover, splices formed in aweb of extremely thin film using a narrow strip of splicing tape have todate proved to be totally unsuccessful in withstanding repeated foldingand tractional forces to which they may be subject, not as a result of alack of strength of the bonded surface but rather through the effect ofshearing forces that are exercised by two lengths of spliced film inwhich the ends are in a touching or to all intents and purposes atouching or butt relationship.

A further significant disadvantage of splices provided in thin filmsthat take the form of a butt joint to which a narrow band of splicingtape has been applied results from the sudden shock which is inevitablyproduced by the excess thickness at the point of splicing when the filmpasses between guide or drive rolls or even in front of a read and/orwrite head in the case where the film is used as an information carrierby application of a magnetic material coating thereto, or during othersuchlike operations on the tape. Similarly, metallization operationswhich are currently carried out on films that have been spliced exhibitvisual discontinuities and other manifestations in the spliced area.

One object of the present invention consists in providing a method and adevice for splicing two lengths of thin film in which accurate joiningof the two portions of film is facilitated and partly automated withoutthe participants in the splice being able to move under the effects ofstatic electricity.

A further object is to provide a splice between two portions of thinfilm which during use is not only as strong when subject to tractionalforces as the unspliced film but which also is as strong, when subjectto alternating bending forces and to general stresses, as the originalfilm whereby if the film does break, it does not break at the splice butrather at another point on the film.

A further object is to obtain a splice in two lengths of extremely thinfilm where the splice itself is as thin as possible. To achieve such athin splice, it should be possible to employ a very thin adhesivesplicing tape which, after application to said thin film, is barelythicker than the spliced film, bearing in mind that splices in thin filmare currently provided using splicing tape which, in the case of verythin films, is some twenty times thicker than the film itself, in orderto obtain sufficient rigidity and mechanical strength from the narrowstrip of splicing tape.

SUMMARY OF THE INVENTION

The invention hence provides a method for splicing a first web of filmor sheet material to a second web thereof comprising the steps ofapplying an end portion of a first web of film to the surface of avacuum table by applying sub-atmospheric pressure or vacuum thereto andmaking a straight transverse cut through said first web by knife meanscooperating with a first transverse groove provided in said vacuumtable, removing the sub-atmospheric pressure below the portion of saidfirst web that has been trimmed off and removing said trimmed-offportion of film, applying the end portion of said second web of filmonto the portion of said vacuum table not covered by said first web andallowing the end of said second web to overlap the previously-trimmedfirst web, the whole surface of said vacuum table being undersub-atmospheric pressure, providing a straight transverse cut throughsaid second web by cooperation of cutting means with a second groove insaid vacuum table parallel to said first groove and adjacent thereto,removing the thus-trimmed portion of said second film from the surfaceof said table together with the portion thereof overlapping said firstweb after, if necessary, removing said sub-atmospheric pressure only inthe part of said vacuum table comprised between said first and secondgrooves, and simultaneously applying to said first and second web endportions an adhesive tape of which at least the portion that faces thegap between said first and second grooves does not contain adhesive, andthen removing said sub-atmospheric pressure over the whole surface ofsaid vacuum table in order to release the spliced webs of film.

According to one feature of the invention, the adhesive tape carries atthe surface thereof two continuous stripes of adhesive which extend upto the region of, but not exactly to the edge of, the lateral sides ofsaid tape where it ceases to be in contact with either of said webportions in order to prevent any overflow of adhesive resulting fromsupplementary spreading of the adhesive during the passage of said tapeover the two film portions to be spliced.

According to another feature, the adhesive tape is covered, on the sidethereof bearing said continuous stripes of adhesive, with a backingstrip or layer in a material exhibiting low adhesion towards saidadhesive, said adhesive tape covered with said backing layer beingprovided in roll form, said roll being unwound onto the facing endportions of the two webs of film to be spliced while removing saidbacking strip immediately prior to applying said adhesive tape onto thetwo facing end portions of said webs. During application of the adhesivetape onto the two end portions of said webs to be spliced, the part ofsaid vacuum table comprised between said first and second grooves ismaintained under sub-atmospheric pressure in order to retain saidadhesive tape firmly pressed onto the end portions of said first andsecond webs.

The invention also provides a device for carrying out splicing, thedevice comprising a roll supplying a web of film material, a roll forwinding a web of film material and a splicing table adapted to beselectively subject to sub-atmospheric pressure or vacuum and having afirst groove therein defining a cutting line over which either of saidfirst or second continuous strips of film can be placed, and means forapplying a splicing tape to unite said first and second webs of film,wherein said splicing table includes two grooves that are parallel andperpendicular to the longitudinal direction of the first and second websof film and being separated by a small spacing from each other, saidsmall spacing being substantially less than the width of said splicingtape, the vacuum table being split into three regions each individuallyadapted to be put under sub-atmospheric pressure and comprising theregion between the two said grooves and two regions at each side of thesaid grooves, said regions being adapted to be linked by valve means tosub-atmospheric pressure generating means whereby each one of said threezones can be individually or simultaneously put under sub-atmosphericpressure in order to retain at least one of said web portions of filmfirmly on said table or to allow removal thereof by cutting off saidsub-atmospheric pressure.

According to another feature of the device, it includes a reel forapplying an adhesive splicing tape to film web portions retained on saidvacuum table by unwinding said adhesive tape therefrom, said applicationreel being rotatably mounted on a support adapted to move in a directionperpendicular to the plane of said vacuum table up to a position whereit no longer hinders the passage of a web of film to a winding unit.

The device can include a carriage able to move along sliding guidingmeans perpendicular to the longitudinal direction of advance of said webof film and which simultaneously carries in a releasable manner, a rollof adhesive tape that is substantially centered on the two grooves ofsaid vacuum table, said carriage being able to move between an operatingposition and a non-operating position, at least one cutting unit adaptedto apply, in said operating position, a knife blade means into at leastone of said grooves in order to cut said web portions of film atpositions corresponding to said grooves whereby said cut web portions offilm are only separated by the gap between said two parallel grooves.The cutting unit includes a blade holder clamping two thin cuttingblades and adapted to pivot about a pivot pin to adopt one of threepositions that are manually locked by a locking means, comprising twoblade cutting positions and a central non-active position. The cuttingunit preferably includes a pivoting arm carrying a press-on roller whichis urged towards the surface of the vacuum table by application ofspring pressure. The pivoting arm can be manually locked in a non-activeposition against the force of the spring means by manual locking means.

Further objects, advantages and features of the invention will becomemore clear from the description of an embodiment thereof which followsand is provided by way of non-limiting example and with reference to theattached drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings:

FIG. 1 is a diagrammatical view in perspective of a device for splicingtwo lengths of thin film using a vacuum table, in accordance with theinvention.

FIG. 2 is a partial front view of the actual vacuum table employed inthe splicing device shown diagrammatically in FIG. 1.

FIG. 3 is a partial side view, partly in cross-section, of a device forsplicing two lengths of film in its operating position with two lengthsof film in the process of being spliced.

FIG. 3a shows detail of FIG. 3 corresponding to the part thereof withincircle A, on an enlarged scale.

FIG. 4 is a detailed view in cross-section taken along line 4--4 of FIG.5a of a film cutting unit and the system for dispensing the adhesivesplicing tape in the device for splicing two lengths of film shown inside view in FIG. 1.

FIGS. 5a and 5b are detailed side views taken in the direction of arrowB in FIG. 3 of the film cutting unit shown in cross-section in FIG. 4 inits respective non-operational position allowing one or several lengthsof film material to pass freely therethrough and its operating positionfor cutting the ends of lengths of film that are to be spliced.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT

FIG. 1 illustrates diagrammatically the method according to theinvention for splicing two webs of thin film. A vacuum box 1 adapted tobe connected to a source of negative pressure, in other words forproviding air vacuum (not shown) carries a vacuum table 2 at its topportion, taking the form of a porous plate carrying two narrow parallelgrooves 3 and 4 designed to guide a cutting blade, as will be explainedbelow.

In the method according to the invention, two ultra-thin webs of film 5and 6 (their minimum thickness can be as low as 0.9 micron but is mostfrequently of the order of several microns) are to be spliced to form acontinuous run, in other words by the establishment of perfect orquasi-perfect alignment of the two webs of film. Before making thesplice, the end portions of the two lengths of film are appliedsuccessively onto the vacuum table 2 which is under negative pressure.End portion 5 is for example the first one to be applied, and iscarefully aligned over the whole surface of table 2, the vacuum pressureensuring that it is firmly held onto the plane surface of the table 2,after which it is cut by a cutting blade (not shown here) which engagesin guide groove 3 in order to provide a neat cut that is strictlyperpendicular to the strip of film 5.

The three parts 2a, 2b and 2c of the vacuum table, respectivelybordering each side of grooves 3 and 4 and lying between grooves 3 and4, are separately linked to a source of negative pressure, consistingfor example of a vacuum pump, via individual valves (reference to FIG. 3will give an idea of the separate means employed for putting the threeparts 2a, 2b, 2c of vacuum table 2 under vacuum). After making thecrosswise cut through film 5, the negative pressure acting on the parts2c and 2b of the vacuum table is removed, followed, if necessary, bysetting of the corresponding part of the vacuum box to a pressureslightly above atmospheric pressure, in other words by blowing airthrough the porous plates of parts 2b and 2c. This makes it possible todetach and remove the offcut or trim left after cutting which is layingon parts 2b, 2c of the table, while the film portion 5 remains firmlyheld onto the part 2a of the table surface that is kept undersub-atmospheric pressure.

With the film 5 now ready for splicing, the end portion of a web of film6 is now brought into exact alignment therewith (in other words fittingit exactly over film 5), this end, prior to cutting, extending beyondgroove 4. The parts 2b and 2c of table 5 are now again put undersub-atmospheric pressure thus causing film 6 to adhere firmly to thetable surface at the parts 2b and 2c thereof while the free end of film6 simply lays on top of film 5 which itself is firmly held onto part 2aof the table surface. Next, the end of film 6 is cut by a knife guidedby groove 4. After shutting off the sub-atmospheric pressure acting ontable portion 2c (and changing over to slight positive pressure if needbe), the trim or offcut of film 6 that was adhering onto vacuum tablepart 2c can be detached from the table surface and then removed alongwith the remainder of the trim laying on top of the already cut film 5.By this means, the two facing ends of films 5 and 6 are provided with aclean cut which accurately is positioned and is strictly perpendicularto the longitudinal direction of the two webs of film that are now heldin perfect alignment on the surface of the vacuum table.

In order to join the two end of films 5 and 6, an ultra-thin adhesivetape is employed which is prepared on a reel of composite material. Thisreel of composite material which is shown diagrammatically in itsposition of use and is indicated generally by reference numeral 7,consists of a wound composite roll 8 (see FIG. 2 as FIG. 1 does not showthe composite structure of the tape).

The composite tape 8 consists of a first strip of thin film 9 in apolymeric material and a second strip 10 in a material which adherespoorly to adhesives, such as a silicone-impregnated backing layer, whichhere is substantially of the same width as the thin film strip, and isseveral times thicker than the thin film. Between the first thin filmstrip 9 and the second backing layer strip 10, the composite materialincludes two parallel layers 11, 12 of an adhesive having considerableadhesive power but exhibiting a far greater tendency to adhere to thepolymeric material of film 9 than to the backing layer 10.

The adhesive is provided in the form of two parallel stripes 11, 12running along the two outer sides of one face of the polymeric materialfilm 9, leaving an adhesive-free region 13 therebetween the width ofwhich is similar to or slightly greater than the distance separating thetwo guide grooves 3, 4. Adhesive that was applied to the backing layer10 gets transferred onto the face of the first strip facing the backinglayer when contact takes place between the adhesive and the surface ofthe first strip 9.

As can be seen in FIG. 1, prior to applying the thin film strip 9simultaneously onto the two facing end portions of films 5 and 6 to bespliced and which are separated by vacuum table portion 2c, the backinglayer 10 is first lifted off from the two adhesive stripes 11 and 12 andfollowing this the thin strip 9 is accurately applied to the two filmportions 5, 6 to be spliced starting from one end of the cut through thetwo films and proceeding to the other end of the cut while progressivelypeeling off the strip of silicone-impregnated backing layer. In thisway, only a short length of the adhesive stripes 11 and 12 is exposedduring the operation of applying the adhesive polymeric strip 9, thusconsiderably reducing the danger of the powerful adhesive materialclinging to some foreign body which might accidently be present, such asdust or other pollutants. As soon as the bonding operation of polymericfilm 9 has been completed up to the other end of the cut end of films 5and 6, the tape 9 is cut and the silicone backing strip 10 can be foldedback over the exposed adhesive stripes 11 and 12 in order to prevent anypossible subsequent pollution thereof. Following this, thesub-atmospheric pressure acting over the whole vacuum table surface isreleased and the projecting two ends of the thin polymeric film 9 aretrimmed transversely to the splices and in alignment with the respectiveedges 5a, 6a and 5b, 6b of the spliced length of film in order toterminate the splicing operation. The two stripes of adhesive 11 and 12are in fact arranged so as to lie at a slight distance from therespective outer longitudinal sides of the adhesive tape 9 and, afterapplication of the adhesive tape to the two webs, to stop slightly shortof the two respective facing ends 5c, 6c of the two portions of splicedfilm 5, 6 whereby the adhesive film can spread slightly under pressurewhen there is contact between tape 9 and the portions 5 and 6 of splicedfilm without the adhesive overflowing beyond the respective edges.

The definitive splice between the two portions of film using thepolymeric tape 9 which is extremely thin (whenever possible, it shouldhave substantially the same thickness as the two web portions of film 5and 6 to be spliced), and a layer of adhesive that is even thinner afterbeing squeezed and drying, makes it possible to provide a splicestructure which, when considered in the longitudinal sense of thespliced web, consists of a splice that is only twice as thick as thefilm to be spliced followed, in the central portion between the twosplices, with a return to the thickness of the original film, this beingfollowed by the second splice which again is only twice the thickness ofthe film, this ensuring that the splices behave perfectly during windingoperations or, when for example the film is used as a backing materialfor a magnetic material coating for passage of a read/write head, or yetagain, during slitting of the wide film into narrower strips. Practicehas shown that the quality and accuracy of the splice are such that itcannot be detected by the naked eye, particularly in the case where theadhesive tape 9 used to provide the splice is of the same material asthat of the two webs of film to be spliced.

In the partial side view of FIGS. 3 and 3a the portions 2a, 2b, 2c ofthe vacuum table together with the crosswise cutting knife guide grooves3 and 4 will be recognized. The composite adhesive tape 8 is wound on adispenser reel 14 carried on a carriage 15 which moves transversely withrespect to the film 5 and 6 to be spliced, on a dual-guiding slide 16,which, in FIG. 3, can be seen in cross-section, and is secured onto astrong cross member 17.

The reel 14 rotates on a central pivot 18 (see also FIG. 4) which issecured parallel to the plane of the vacuum table 2, on an upright 19 ofthe frame structure of carriage 15. The lower portion of upright 19carries a cutting unit 20 arranged above the vacuum table 2 but onlyseparated by a very small distance therefrom, this being shown ingreater detail in FIGS. 4 and 5.

FIG. 3 also shows a cross-section through the vacuum box 1. Threeseparate chamber 21, 22, 23 are defined below the porous plate 2 of thevacuum table and each of these is connected by an airtight connector21a, 22a, 23a and flexible or rigid conduits to valves 21b, 22b, 23bwhich can either be connected to a source of sub-atmospheric pressure(vacuum pump) or to atmospheric pressure to release a vacuum, or even,if necessary, to a source of compressed air to aid in the lifting off ofportions of .film that are adhering firmly to the vacuum table. Thevacuum box 1 which, for example, is a metal casting, is carried by aframe structure 24 which includes, apart from cross member 17 carryingthe slide 16, strengthening members (see cross member 25) an auxiliarywinding roller 26 rotatably mounted on extension members 27, togetherwith guide rolls 28, 29 and 30 for the film, roll 29 having an elastomerouter surface.

The structure of the vacuum table 2 in the critical region indicatedinside circle A of FIG. 3, is shown on a much larger scale in FIG. 3aenabling the two grooves 3 and 4 to be seen, these having a rectangularcross-section separating the vacuum table into three successive regions2a, 2b, 2c. A knife 31, and, respectively, 32 can be engaged into eachof these grooves in order to cut the film which is firmly applied bysuction onto the porous vacuum table 2.

In FIG. 3a, the film 6 is shown as having already been unwound via guideroll 29 until all spare film from the roll of film that preceded roll 33has been wound off. The spare film end 6 is then cut by knife 32, itsend edge 6c portion being "stuck" to portion 2b of vacuum table 2 by thesub-atmospheric pressure prevailing therebelow. The other portion offilm, 5, which is to be spliced to portion 6 of the film is unwound froma new large diameter roll 33. Before making the splice, the film portion5 is passed under guide roller 28 before moving on to the vacuum table 2of which only chamber 23 is held under sub-atmospheric pressure. The endportion of film 5 can readily slide over vacuum table 2 to a positionwhere it overlaps the end portion of film 6, careful positioning beingcarried out until film portions 5 and 6, which, in principle, have thesame width come into exact alignment with each other, several turns offilm portion 5 being rewound onto auxiliary roll 26 and the filmadequately tensioned. After this, vacuum chambers 21 and 22 are putunder sub-atmospheric pressure by operating valves 22b and 21b whichcauses the film portion 5 to firmly "stick" onto the vacuum table in theregions 2a and 2c. It is now possible to make a transverse cut throughthe film portion 5 by means of knife 31 which moves along inside groove3, with the several turns of film wound onto auxiliary roll 26 remainingin place as offcut or trim. As a simplified alternative, to reduce thelength of offcut at the end of film portion 5, the latter can bepositioned manually and tensioned, this solution requiring however theintervention of highly skilled labor in order to guarantee the samesplice quality.

In FIG. 3a, the two knives or blades 31 and 32 have been shownsimultaneously cutting the film and leaving portions of offcut or trim5d and 5e but is also possible, as shown in FIGS. 5a and 5b, to onlybring knife 31 into position. The portions of offcut 5d and 5e areremoved after chamber 22 is no longer subject to sub-atmosphericpressure, by operating valve 22b (and blowing if necessary), the chamber21 being kept under sub-atmospheric pressure in order to retain the endportion of film 5. The two end portions of films 5 and 6 are thus firmlyheld in position ready to receive the adhesive tape 9 using the methodillustrated, as regards its initial steps, in FIG. 2, and describedabove with reference to FIG. 1. With the film portions 5 and 6 nowspliced by means of polymeric tape 9 and its two stripes of adhesive 11and 12, winding via guide roll 29 can now be restarted.

FIG. 5b shows film portion 5 during a cutting operation. The framemember 19 carries an arm 33 which rotates about pin 33a and which isurged by means of a flat spring 34 towards film portion 5 (or 6) inorder to apply a small press-on roller or hold-down cylinder 35 thereto.A knife support 36 which can rotate about a pivot pin 36a integral witha plate 36b screwed onto frame member 19, carries a knife holder 37which retains the knife blades 31 and 32 which are 25 axially separatedby a distance d, which corresponds to the distance between the grooves 3and 4. In FIG. 5b, blade 32 is engaged in groove 4 for cutting filmportion 6.

FIG. 5a shows the non-operating position of cutting unit 20. A pin 38with a knurled head 38a has been engaged in a hole 39 (see FIG. 5b) of aretaining plate 40, in order to hold press-on roller 35 away from thefilm 5, 6 which moves at high speed during winding. Similarly, a pin 41with a knurled head 42 has been engaged into the central hole 43 of aseries of three holes 43, 44, 45 the two outer holes of which, 44 and 1045, are used for locking the cutting positions of the blades 31, 32 byengagement of pin 41 therein.

Perfect guiding, obtained by the two guiding surfaces of slide 16, ofknife 31 or 32 in grooves 3 and 4 while film portions 5, 6 are kept helddown by suction applied at both sides of the grooves 3 and 4, as well asperfect guiding of reel 14 which enables the adhesive tape 9 to beapplied strictly perpendicular to the axis of film portions 5 and 6,ensures that the adhesive tape 9 is applied accurately to the endportions of film which are firmly held in position by sub-atmosphericpressure.

The present invention is obviously not limited to the embodiments whichhave been described and illustrated above but may be subject to numerousvariations available to those skilled in the art without this howeverleading to a departure from the scope of the invention.

What is claimed is:
 1. A method for splicing a first web of film orsheet material to a second web thereof comprising the steps of: applyingan end portion of a first web of film to the surface of a vacuum tableby applying sub-atmospheric pressure thereto and making a straighttransverse cut through said first web by knife means cooperating with afirst transverse groove provided in said vacuum table,removing thesub-atmospheric pressure below the portion of said first web that hasbeen trimmed off and removing said trimmed-off portion of film, applyingthe end portion of said second web of film onto the portion of saidvacuum table not covered by said first web and allowing the end of saidsecond web to overlap the previously-trimmed first web, the wholesurface of said vacuum table being under sub-atmospheric pressure,providing a straight transverse cut through said second web bycooperation of cutting means with a second groove in said vacuum tableparallel to said first groove and adjacent thereto, removing thethus-trimmed portion of said second film from the surface of said tabletogether with the portion thereof overlapping said first web after, ifnecessary, removing said sub-atmospheric pressure only in the part ofsaid vacuum table comprised between said first and second grooves, andsimultaneously applying to said first and second web end portions anadhesive tape of which at least the portion that faces the gap betweensaid first and second grooves does not contain adhesive and thenremoving said sub-atmospheric pressure over the whole surface of saidvacuum table in order to release the spliced webs of film.
 2. A methodaccording to claim 1, wherein said adhesive tape carries at the surfacethereof two continuous stripes of adhesive which extend up to the regionof, but not exactly to the edge of, the lateral sides of said tape whereit ceases to be in contact with either of said web portions in order toprevent any overflow of adhesive resulting from supplementary spreadingof the adhesive during the passage of said tape over the two filmportions to be spliced.
 3. A method according to claim 1, wherein saidadhesive tape is covered, on the side thereof bearing said continuousstripes of adhesive, with a backing strip or layer in a materialexhibiting low adhesion towards said adhesive, said adhesive tapecovered with said backing layer being provided in roll form, said rollbeing unwound onto the facing end portions of the two webs of film to bespliced while removing said backing strip immediately prior to applyingsaid adhesive tape onto the two facing end portions of said webs.
 4. Amethod according to claim 1, wherein during application of said adhesivetape onto the two end portions of said webs to be spliced, the part ofsaid vacuum table comprised between said first and second grooves ismaintained under sub-atmospheric pressure in order to retain saidadhesive tape firmly pressed onto the end portions of said first andsecond webs.
 5. A device for splicing first and second webs of film orsheet material together comprising a roll supplying a web of filmmaterial, a roll for winding a web of film material and a splicing tableadapted to be selectively subject to sub-atmospheric pressure and havinga first groove therein defining a cutting line over which either of saidfirst or second continuous webs of film can be placed, and means forapplying a splicing tape to unite said first and second webs of film,wherein said splicing table includes a second groove that is parallel tosaid first groove, said first and second grooves being perpendicular tothe longitudinal direction of said first and second webs of film andbeing separated by a small space from each other, said small space beingsubstantially less than the width of said splicing tape, said vacuumtable being split into three regions each individually adapted to be putunder sub-atmospheric pressure and comprising the region between the twosaid grooves and two regions at each side of the said grooves, saidregions being adapted to be linked by valve means to sub-atmosphericpressure generating means whereby each one of said three zones can beindividually or simultaneously put under sub-atmospheric pressure inorder to retain at least one of said web portions of film firmly on saidtable or to allow removal thereof by releasing said sub-atmosphericpressure.
 6. A device according to claim 5, wherein it includes a reelfor applying an adhesive splicing tape to film web portions retained onsaid vacuum table by unwinding said adhesive tape therefrom, saidapplication reel being rotatably mounted on a support adapted to move ina direction perpendicular to the plane of said vacuum table up to aposition where it no longer hinders the passage of a web of said film toa winding unit.
 7. A device according to claim 5 wherein it includes acarriage able to move along sliding guiding means perpendicular to thelongitudinal direction of advance of said web of film and whichsimultaneously carries in a releasable manner, a roll of adhesive tapethat is substantially centered on the two grooves of said vacuum table,said carriage being able to move between an operating position and anon-operating position, at least one cutting unit adapted to apply, insaid operating position, a knife blade means into at least one of saidgrooves in order to cut said web portions of film at positionscorresponding to said grooves whereby said cut web portions of film areonly separated by the gap between said two parallel grooves.
 8. A deviceaccording to claim 7, wherein said cutting unit includes a blade holderclamping two thin cutting blades adapted to pivot about a pivot pin toadopt one of three positions that are manually locked by a lockingmeans, comprising two cutting positions and a central non-activeposition.
 9. A device according to claim 7, wherein said cutting unitincludes a pivoting arm carrying a press-on roller which is urgedtowards the surface of said vacuum table by spring pressure.
 10. Adevice according to claim 9, wherein said pivoting arm is manuallylockable in a non-active position against the urging force of saidspring means by manual locking means.